Don's Tools · Developers · Cron Builder

Cron builder

Write a cron schedule and instantly see what it means and when it next runs. Nothing is uploaded.

Presets
min
hour
day (m)
month
day (w)
Works offline: the expression is described and the next run times are worked out in your browser, with nothing uploaded. Standard 5-field cron is supported (minute, hour, day of month, month, day of week) with ranges, lists and steps. Times shown are in your local timezone.
Cron Builder is a free developer tool that explains cron expressions in plain English and shows the next run times, entirely in your browser with nothing uploaded. It supports standard five-field cron with stars, ranges, lists and steps, offers common presets, and lists the next five firing times in your local timezone.

Frequently asked questions

Is anything uploaded?

No. The expression is described and the next run times are worked out entirely in your browser, with nothing uploaded. It works offline once loaded.

Which cron format does it use?

Standard 5-field cron: minute, hour, day of month, month and day of week, supporting stars, ranges like 1-5, lists like 1,15 and steps like every-five written as the slash form.

How are the next run times calculated?

It scans forward minute by minute from now and lists the next five matching times in your local timezone, exactly as a scheduler would fire them.

How are day-of-month and day-of-week combined?

Following the usual cron rule, if both are set the job runs when either matches; if only one is set, only that one applies.

Why might it say no upcoming runs?

Some expressions can never match, such as February 30th. If nothing matches within the next few years, that is reported instead of a run list.